1. Field of the Invention
This invention relates to a method of and a service node for providing services in an intelligent communications network.
2. Related Art
Before the advent of the stored program controlled (SPC) exchange, the Public Switched Telephone Network (PSTN) comprised electromechanical exchanges, such as Strowger and Crossbar exchanges, and electronic exchanges, such as TXE2 and TXE4 exchanges. However, even the most advanced of these types was only capable of performing a limited number of functions over and above merely switching a call, i.e. making a connection between an incoming channel or line and an outgoing channel. Furthermore, such additional functions were limited to operations for improving the performance of the network, for example, repeat attempt at reaching a destination number via an alternative outgoing route in the event that the first-choice route is busy.
SPC exchanges enabled customers to control various supplementary services via signals entered on their telephone keypad using the * and # buttons. However, the introduction of a new service, or the modification of an existing service, meant that the control program had to be updated in each of the SPC exchanges.
The current concept of an intelligent communications network is based on a core of interconnected Digital Main Switching Units (DMSU's), with local exchanges connected to the DMSU's (usually with each local exchange connected to two DMSU's for network resilience in the event of an DMSU failure), and with services being provided and controlled by discrete service nodes at various positions in the network.
Each service node is connected to an DMSU of the network, which recognises service access digits dialled by a customer and routes the call to the service node for the provision of the requested service for the customer.
As an example of the abovementioned concept, an Intelligent Network testbed architecture is disclosed in the article "Experiences in Prototyping the Intelligent Network", by Peter O'Reilly, Hing Fai (Louis) Chong, Russell Sivey and Lawrence Lattanzi; IEEE Global Telecommunications Conference, Nov. 29 to Dec. 2, 1993; Volume 1 of 4, pages 1923 to 1930. In this architecture, a Service Control Point (SCP) is connected by a signalling link, known to telecommunications engineers as a C7 or SS7 link, to a switch. The SCP is also connected by a data link for call control commands and messages to an intelligent peripheral (IP) containing resources, such as announcements and digit collection. The IP is connected to the switch by a communications link providing a voice path.
The article "Service Script Interpreter, An Advanced Intelligent Network Platform" by Paul van Hal, Jan van der Meer and Nael Salah, published in Ericsson Review No. 1, 1990, pages 12 to 22, describes various network elements of Ericsson's Intelligent Network Architecture. One of these elements is an Intelligent Peripheral (IP) which is a collection of versatile and cost-effective equipment allowing communications between the Intelligent Network and its subscribers. The IP can send a number of different announcements to subscribers and receive digits from dual tone multi-frequency (DTMF) telephones, the announcements being either of a fixed format or having a variable part. The IP can be provided as a separate node accessible by several Service Switching Points (SSPs) through which it is controlled by commands from respective Service Control Points. Digits received by the IP are sent to the controlling SCP, through the associated SSP, for analysis.
In International Application Number PCT/US91/03086 (Publication Number WO 91/17616) a disk system stores voice message segments (VMS), each VMS having an identifying address number. When voice messages are to be played to subscribers, Send Message commands are sent via a voice message management module (VMMM) to an input/output processor which refers to a look-up table, by which it converts the Message Number to a respective sequence of VMSs, and retrieves the sequence of VMSs from the disk system. The VMM then sends corresponding commands, including fields designating the Channel Number, Call ID and Message Number of the message to be sent, into a command queue of a buffering interface module which receives the respective sequences of VMSs and inserts them into the required channel of a multiplexed transmission link to the switch.
In the article "SCP Development in a multi-processor UNIX environment" by S. Hollywood, Proc Int Council for Computer Communications, May 4-6, 1992, Tampa, pages 278-287, when an application passes a request to the Service Logic Execution Environment (SLEE) for, e.g., playing an announcement, it passes not only the request but the current call status or call context data. When the external request completes, the SLEE can send the resulting message and the call context data to any available application process for that service, since the package of data contains all the information for the call